There are so many different kinds of expertise, you can't have everything in house. The problem is that now you are going to have to hire someone for something that you are not qualified to do yourself, which almost automatically implies that you are not qualified to make that hire either. So everybody plays it safe and they hire the 'big names' because those have social proof, no matter how crap the actual interaction.
Yes, that's a more detailed way of saying what I mean, but without the snark against "the free market". The value provided by the big 4 is based on a universal acceptance of "play it safe, cover your ass" instead of "we provide quality advice". The big 4 have realised this, as near, captive market, and lowered their output accordingly.
